3 BARS on the MIC Selector on the ACP.
 

What is the significance of the 3 BARS which illuminate, when a transmitter is selected for transmission on the ACP. It's vertical on the 737 and horizontal on the A320.

http://www.b737.org.uk/images/aspbuttons.jpg

http://www.jaasimulators.com/wp-cont...80006142_n.jpg

I would imagine this is purely design.
And Boeing and Airbus would always be opposite. On the Airbus overhead panel up is on and down is off. Boeing is round the other way!

Thanks applecrumble... wanted to know why the 3 bars.

I'd hazard a guess that there's no significance to it being 3 bars, regardless of orientation. You simply need to be able to look down at the panel and see something which indicates which button is selected..TBH it could just as easily be dots or stars, whatever......

FWIW on some Boeings you simply get a backlit illuminated "MIC" where appropriate.

After more than 7000 hours on the Airbus and 3000 on the Boeing I honestly never noticed..it's just a light.

Bar 1, aviate. Bar 2, navigate. Bar 3, communicate.

On Boeings, on is toward the windshield and off away from. Unless the airplane was built for TWA.

RE 3 Bars - I expect that is "functional design" - make the MIC/TRANSMIT selection buttons quickly distinguishable from all the other pedestal lights/buttons at night.

Alternatively - could be simply 3 LEDS for redundancy, in case one burns out. But the fact that the pattern (3 bars, regardless of orientation) is common across B and A makes the first idea more likely. Embraer uses one bar - but still a bar (EMB reception controls have round indicator lights).

Switch direction is also an option on Airbus aircraft.

Boeing: ON>Forward>Go! :D :ok:

PS The threebars in my Boeing are horizontal! :eek:

Or Lufthansa or any number of carriers that made operating a diverse fleet of 737-200s a nightmare.

I've got four......:}

Coat, Hat, door......:8

pattern_is_full thanks for your reply. From what I figure... the 3 bars symbolises the word MIC.

How did you find that out?

What about the "ROPHONE"?

I used to fly freight in old 707s from a variety of sources with no two alike. We had switches going both ways.